At some point older versions will not be supported and have unpatched security vulnerabilities, module updates won't run on older versions of Perl etc.

You should take the opportunity to work out some form of company wide regular upgrade process and to make it as painless as possible. I'm not sure about the benefits of being right on the leading edge, but you shouldn't be too far behind it.

Update: Some people have pointed out that releases are customised and may be difficult to upgrade. There is an argument for leaving the system Perl unaffected and having an independent site Perl, which is hopefully kept up to date.

If you spot any bugs in my solutions, it's because I've deliberately left them in as an exercise for the reader! :-)